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The cold world of skimo & alpine climbing

Monday, February 14, 2011

The Curious Case of the Commercial Umbilical Strengths?

Better said, "Who knows what they will actually hold?"

I guess I am not surprised when I look at the inability of Petzl to have a consistent umbilical attachment point incorporated into all their technical tools. While in comparison, BD builds and then load tests theirs to 1500# or better. Of course neither their umbilical or anyone leashes will take 1500#. Grivel? They want you to tie into a plastic part on some of their tools! The rest of the tool business? It is no better or worse.

Just a small case study of the extremes in the ice climbing equipment world.

Why we as a climbing community put up with this kind of nonsense is truly stupefying however.

From Left to right:
BD Sprinner leash, old style Grivel Spring leash and a Metolius FS Mini Wiregate

BD flat steel mini biner is good for 1500# or more but 2Kn (450#) rated by the UIAA tag on 13mm (1/2"?) tube webbing. (1/2" nylon tube was rated @ 1800# in the old Chouinard catalog)

Th nylon webbing is likely to always be the weak link on any umbilical.

2kn is the UIAA requirement for leashes. What the hell are they thinking when they write that kind of requirement when it gets applied to umbilicals?

Black Diamond sez:

"Just tested this to 800lbs (single leg of the Spinner leash). No damage to the 4mm cord or our steel clip (production quality with more tumbling to the part); the bungee webbing breaks first. Then pull tested our steel biner clipped to 5mm cord, this went to 1600lbs before the cord broke."

More? This after my earlier comments about umbilicals "being fashionable" and not being designed specifically for the use.

"The steel clip on the spinner leash is anything but fashionable. If I made it out of aluminum it would be a lot lighter and weaker (hence more fashionable), and if I made the gate opening smaller and the gate shorter, it would be a lot stiffer for a given diameter of wire. The strength of that clip is somewhere north of 3000lbs (I don't know how strong it really is because everything I have tested it with broke first) ."

Of course no accounting for the fact that the BD Spinner leashes have the nasty and well know habit of popping off at any given moment.

I've no clue what the Grivel is actually good to strength wise. But the same biner was sold as a key chain holder. I have blown the sheath on 4mm cord connecting a single side strand of the Grivel. Biner and webbing seem unharmed. So better than the 3Kn that is stamped in the Grivel biner I suspect. Grivel went to a mini locking boner early on. They might be on to something since Grivel was the first company to offer a commercial umbilical.

Metolius FS Mini Wiregate biner is engraved is 22Kn (4950#) and a good bit heavier and bigger physically in every way as well.

By the "feel" of it the original Grivel wire gate biner (2.5mm wire) has at least twice the gate opening resistance as the BD (2.4mm wire) and easily 3 times the opening resistance of the Metolius mini biner (2.2mm wire).

Some of this goes right along with plastic racking biners (that break or open consistently enough to drop racks) and umbilicals that are only required to take a 450# load by the UIAA requirement. That as we all know, on occasion, are required to catch full size falling bodies. What the hell is the UIAA thinking? How about a design and strength requirements that incorporates the actual use?

Umbilicals have been in use at least 30 years now in the ice climbing community. This isn't a new idea or use. Umbilicals were pulling the spikes through water rotted laminated bamboo on Chouinard Zeros back then. May be it is about time the rest of the world catches up with what we actually do require.

Problem is I don't know the strength of any of this stuff including the webbing. I am sure BD has numbers but they are saying 2KN. It may not be normal tube nylon we are use to. BD doesn't really look like it and my older Grivels I don't think they are still making in 9/16 or bigger stuff. The biners aren't the issue although the swivel might be. But I really have no clue which seems kinda silly that we all don't just know what this stuff is good for. Why anyone woudl build climbing gear below 1500# pull strength is beyond me.

I'm using the FS mini's combined with 1/2" tubular "mil-spec" webbing (5kN) for a simple (and very cheap) umbilical set up.

I reckon one of the plus's of using the FS mini's would be that in a pinch you're always guarenteed to have 2 extra full-strength carabiners for anchors/protection/etc. nice to have multiple applications for the same piece of kit

What does it matter how strong thewy are? Why the hell would you hang from you umbicals?! They are designed to stop you from dropping a tool not arrest a fall. I can think of nothing worse than a spring loaded axe!

It seems the sling is the weakest link. Did I read it correctly - sling broke at 800lb (3.6kN)? This makes sense because the webbing is thinner than standard 0.5" milspec - which is quoted as having tensile of 4.5kN according to mec website.

This is definitely not strong enough to intentionally hang from, but no matter how you adjust it or what your height is, it does not seem practical to intentionally hang from anyhow - too much extension from the stretch plus harness riding up.

However, it would be nice to have some confidence that it will hold an unexpected slip. Has anyone seriously fallen onto one?

The 3.6kN sounds decent enough to reliably hold body weight. Bodyweight is only 0.8kN (80kg). The problem though is that it is extremely static, so if you were to cleanly fall onto it from more than a few inches, the static impact is huge and likely to either shear the tool out or break the webbing. A clean 1ft fall onto a static sling can apparently generate close to 10kN impact force.

It would be really nice if it could be made more dynamic somehow. I've been experimenting with attaching it to my harness with a screamer aid (1.5kN activation) - but it is a little awkward. Would be even better if a few load limiting stitches could be built directly into it somehow. Anyone have thoughts on this?